I believe your question is about "gerunds" being "nouns".
A "gerund" is any verb + "ing". A "gerund" can act both as a verb and as a noun in a sentence. Here are examples of using a gerund as a noun,
1. "walking is good for your health." --- Here "walking" is the gerund, and it's also the subject of the sentence, just like any other noun could be.
2. "Jane enjoys waking up early." --- Here the gerund is "waking up", and it's the object of the sentence, again, like any other noun.
I hope this helps!